The present invention pertains to a material handling system and, in particular, to a technique for evaluating the material handling system, including, but not limited to, determining defects in the material handling system. The invention can be applied to positive displacement shoe and slat sorters, automated storage and retrieval systems, cross-belt sorters, tilt tray sorters, and the like.
Material handling systems tend to be very large systems. In the case of positive displacement shoe and slat sorters, by way of example, the conveying surface can extend for hundreds of feet. If the material handling system goes out of specification, it may be difficult to determine with precision where the condition exists. This is particularly troublesome if there are numerous deviations from specification. While any one of these may not significantly degrade operation of the material handling system, their cumulative affect can be very detrimental.
Such out of specification condition can occur at different times during the life of the material handling system. It can occur while the material handling system is being installed. It can also occur after the system has been in operation for many years. This can be the result of wear of the components, from debris accumulating in the system or it can be the result of the surface on which the system is mounted being subject to movement, just to name a few. The latter situation may result from the mounting of the material handling system on an overhead platform which is quite common; as such platforms are prone to movement over the lifetime of the material handling system.
The use of tools for measuring and monitoring the distance between moving objects and support tracks or rails of material handling systems is known. For example, U.S. Pat. No. 7,081,824 issued to Gillespie discloses a system adapted to detect the linear displacement of a wheel set of a railroad bogie relative to the tracks on which the bogie rides. The use of measurement devices for measuring the distance between traveling slat members and lateral tracks in positive linear displacement conveyor sortation systems has also been described. The use of distance sensors for measuring distance to a rail or restraining surface, however, provides only limited information regarding the condition of a material handling system.